Flashcards in Lecture 6 Deck (10)
What is membrane electrical polarization?
All cells having a net electrical charge across its membrane
When is a membrane polarized?
When a neuron is not stimulated (at rest)
— no impulse to carry or transmit —
What happens at resting stage?
Has negative charge inside
-60 to -100mV - depending on cell type (resting MP)
Determined by concentration gradients of ions across the membrane and by membrane permeability
Resting cells have negative electrical potential inside the cell
What is happening inside the cell at resting stage?
Channels remain closed
NA/K powered by ATP maintain gradient - RMP
What happens at depolarization?
Na channels opened and K channels closed.
Neuron reacts to stimulus - MP changes , action potential generated
NA/K channels open, and NA flows in making the cell more positive or less negative
What happens at repolarization?
Returning the membrane potential to a negative value after the depolarization phase
Repolarization results from the movement of positively charged potassium ions out of the cell
How does NA/K impact water balance?
Osmolarity determines the amount of water inside the cell
Without the pump, intracellular osmolarity would exceed extracellular osmolarity at electrochemical equilibrium
Water would rush into the cell and the cell would burst
Eventually, both channels will be closed, and active transport takes over to return the cell to its resting state
During active transport
Na+ are carried out of the cell and
K+ are carried into the cell
Most important ions?
Na+, K+, Cl– and Ca++
Is the difference between intra and extracellular ions negative or positive?
There is a negative difference between the intracellular and the extracellular compartments
The interior of the membrane (nerve cell) is electrically negative in relation to the exterior